Liquid crystal display device and method for producing the same

ABSTRACT

Provided are a liquid crystal display device that suppresses occurrence of drop marks during production without degrading various properties, such as dielectric anisotropy, viscosity, nematic phase upper limit temperature, rotational viscosity (γ 1 ), and ghosting property, and a method for producing the liquid crystal display device. 
     A liquid crystal display device  10  of the present invention includes a liquid crystal composition layer  13  sandwiched between a first substrate  11  and a second substrate  12  and vertical alignment films  16  and  17  that contain a polymer of a polymerizable compound having a polyimide skeleton as a main chain and a crosslinkable functional group as a side chain. The liquid crystal composition constituting the liquid crystal composition layer  13  contains compounds represented by general formulae (I) and (II).

TECHNICAL FIELD

The present invention relates to a liquid crystal display device usefulas a constitutional member of a liquid crystal television or the likeand a method for producing the liquid crystal display device.

BACKGROUND ART

Liquid crystal display devices are used in watches, calculators, variousmeasuring instruments, automobile panels, word processors, electronicnotepads, printers, computers, televisions, clocks, advertising boards,etc. Representative examples of the types of liquid crystal displays area twisted nematic (TN) type, a super twisted nematic (STN) type, avertical alignment (VA) type that uses thin film transistors (TFTs), andan in-plane switching (IPS) type. The liquid crystal compositions usedin these liquid crystal display devices are required to be stableagainst outer factors such as moisture, air, heat, and light, stay in aliquid crystal phase in a temperature range as wide as possible aboutroom temperature, exhibit a low viscosity, and operate at low drivingvoltage. A liquid crystal composition is constituted by several toseveral tens of compounds in order to optimize the dielectric anisotropy(Δ∈), refractive index anisotropy (Δn), etc., for individual liquidcrystal display devices.

In VA-type displays that are widely used in liquid crystal televisionsand the like, a liquid crystal composition having a negative Δ∈ is used.Meanwhile, for all drive types, low-voltage driving, high-speedresponse, and a wide operation temperature range are desired. In otherwords, the absolute value of Δ∈ is required to be high, the viscosity(η) is required to be low, and the nematic phase-isotropic liquid phasetransition temperature (T_(ni)) is required to be high. Also, there isneed to adjust Δn of the liquid crystal composition to be in anappropriate range that suits the cell gap since the product Δn×d of Δnand a cell gap (d) is set. Moreover, high-speed response is importantfor liquid crystal display devices applied to televisions and the likeand thus a liquid crystal composition having a low rotational viscosity(γ₁) is desired.

Multi-domain vertical alignment (MVA)-type liquid crystal displaydevices which are a type of VA displays with improved viewing anglecharacteristics are now widely used. In this liquid crystal displaydevice, projecting structures are formed on a substrate to divide apixel so that the liquid crystal molecules are aligned in pluraldirections. A MVA liquid crystal display device is advantageous in termsof viewing angle characteristics but has a problem in that liquidcrystal molecules respond at different speeds between the portion nearthe projecting structure on the substrate and the portion remote fromthe projecting structure and thus the overall response speed has beeninsufficient due to the liquid crystal molecules that are remote fromthe projecting structure and slow in response. There has also beendegradation of transmittance caused by the projecting structure. Inorder to address these issues, polymer sustained alignment (PSA) liquidcrystal display devices (an example of which is a polymer stabilized(PS) liquid crystal display device) have been developed to provideuniform pretilt angles within each domain of a pixel without formingnon-transmitting projecting structures in a cell, which is differentfrom a typical MVA liquid crystal display device. A PSA liquid crystaldisplay device is produced by adding a small amount of a reactivemonomer to a liquid crystal composition, introducing the liquid crystalcomposition to a liquid crystal cell, and polymerizing the reactivemonomer in the liquid crystal composition by irradiation with an activeenergy ray. Accordingly, appropriate pretilt angles can be provided inthe divided pixel, and, as a result, improved contrast brought about byimproved transmittance and a high-speed responsiveness caused by auniform pretilt angle can be achieved (for example, refer to PTL 1).However, in a PSA liquid crystal display device, a reactive monomer mustbe added to a liquid crystal composition and this has caused manyproblems in active-matrix liquid crystal display devices that require ahigh voltage holding capacity. There has been another problem of displayfailure such as ghosting.

A method with which the drawbacks of the PSA liquid crystal displaydevices can be overcome and a uniform pretilt angle is provided toliquid crystal molecules without contamination by foreign matter otherthan the liquid crystal materials in the liquid crystal composition hasbeen developed. According to this method, the alignment film materialsuch as polyimide is designed to have a side chain reactive toultraviolet light or the like and an alignment film is formed by usingthis material. After a liquid crystal composition is introduced into aliquid crystal cell, an active energy ray is applied while applying avoltage between electrodes so as to polymerize a reactive monomer in thealignment film (for example, refer to PTL 2 and PTL 3).

As the size of the screen of liquid crystal display devices becomeslarger, the method for producing liquid crystal display devices hasundergone significant changes. That is, since the conventional vacuuminjection method requires a long time to produce large-size panels, aone-drop-fill (ODF)-type production method has become the mainstreamtechnology for producing large panels (for example, refer to PTL 4).Because this method involves a shorter injection time compared to thevacuum injection method, it has become the mainstream method for liquidcrystal display device production. However, drop marks formed bydropping the liquid crystal composition remain in the liquid crystaldisplay device while retaining their shapes even after fabrication ofthe liquid crystal display device. It should be noted that the dropmarks are defined as a phenomenon that the trace left by dropping theliquid crystal composition appears as white marks in black display. Inparticular, according to the method with which a pretilt angle isprovided to liquid crystal molecules by designing the alignment filmmaterial to have a side chain reactive to ultraviolet light or the like,substituents having reactivity remain in the alignment film duringdropping of the liquid crystal composition onto a substrate. Thus, theproblem of drop marks readily occurs. In general, the occurrence of dropmarks frequently depends on the choice of the liquid crystal materialand the exact cause thereof is not clear.

There has been disclosed a method for suppressing drop marks, in which apolymerizable compound mixed into a liquid crystal composition ispolymerized to form a polymer layer in a liquid crystal compositionlayer so as to suppress the drop marks that occur in relation with thealignment control film (for example, refer to PTL 5). However, thismethod has a drawback in that ghosting occurs due to the reactivemonomer added to the liquid crystal composition and that the effect ofsuppressing drop marks is insufficient as with the PSA method and thelike. Thus development of a liquid crystal display device with whichghosting and drop marks are less likely to occur while maintaining basiccharacteristics needed for liquid crystal display devices has beendesired.

CITATION LIST Patent Literature

-   PTL 1: Japanese Unexamined Patent Application Publication No.    2002-357830-   PTL 2: Japanese Unexamined Patent Application Publication No.    2011-95696-   PTL 3: Japanese Unexamined Patent Application Publication No.    2011-95697-   PTL 4: Japanese Unexamined Patent Application Publication No.    6-235925-   PTL 5: Japanese Unexamined Patent Application Publication No.    2006-58755

SUMMARY OF INVENTION Technical Problem

The present invention has been made under the above-describedcircumstances. An object of the invention is to provide a liquid crystaldisplay device that suppresses occurrence of drop marks duringproduction without degrading various properties, such as dielectricanisotropy, viscosity, nematic phase upper limit temperature, rotationalviscosity (γ₁), and ghosting property, and a method for producing theliquid crystal display device.

Solution to Problem

To address these challenges, the inventors of the present invention haveinvestigated on various combinations of liquid crystal compositions andmethod for providing pretilt angles to the molecules in liquid crystaldisplay devices and found that these challenges can be overcome by usinga particular liquid crystal composition in combination with a techniqueof polymerizing a reactive monomer in a vertical alignment film byapplying an active energy ray while applying a voltage betweenelectrodes after a liquid crystal composition is introduced into aliquid crystal cell. Thus, the present invention has been made.

In other words, the present invention provides a liquid crystal displaydevice comprising a first substrate that includes an electrode, a secondsubstrate that includes an electrode, and a liquid crystal compositionlayer sandwiched between the first substrate and the second substrate,in which liquid crystal molecules in the liquid crystal compositionlayer are controlled by applying charges between the electrode of thefirst substrate and the electrode of the second substrate substantiallyvertically to the first substrate and the second substrate. A verticalalignment film, which controls an alignment direction of the liquidcrystal molecules in the liquid crystal composition layer to besubstantially vertical to a surface of the first substrate and a surfaceof the second substrate that are adjacent to the liquid crystalcomposition layer, is disposed on at least one of the first substrateand the second substrate, the vertical alignment film contains a polymerof a polymerizable compound having a polyimide skeleton as a main chainand a crosslinkable functional group as a side chain, and a liquidcrystal composition constituting the liquid crystal composition layercontains a compound represented by general formula (I)

(In the formula, R¹ and R² each independently represent an alkyl grouphaving 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms,an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy grouphaving 2 to 8 carbon atoms; A represents a 1,4-phenylene group or atrans-1,4-cyclohexylene group; l represents 1 or 2; and when l is 2, thetwo A may be the same or different from each other) and a compoundrepresented by general formula (II)

(In the formula, R³ represents an alkyl group having 1 to 8 carbonatoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy grouphaving 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbonatoms; R⁴ represents an alkyl group having 1 to 8 carbon atoms, analkenyl group having 4 to 8 carbon atoms, an alkoxy group having 1 to 8carbon atoms, or an alkenyloxy group having 3 to 8 carbon atoms; Brepresents a 1,4-phenylene group or a trans-1,4-cyclohexylene group; mrepresents 0, 1, or 2; and when m is 2, the two B may be the same ordifferent from each other).

The present invention also provides a method for producing a liquidcrystal display device, the method comprising applying a verticalalignment material to at least one of a first substrate including acommon electrode and a second substrate including a pixel electrode, thevertical alignment material containing a compound that has athermosetting polyimide or soluble polyimide skeleton as a main chainand a crosslinkable functional group as a side chain; heating theapplied vertical alignment material to form an alignment film;sandwiching a liquid crystal composition between the first substrate andthe second substrate; irradiating the alignment film with an activeenergy ray while applying a voltage between the common electrode and thepixel electrode to polymerize a polymerizable compound in the alignmentfilm. The liquid crystal composition contains a compound represented bygeneral formula (I)

(In the formula, R¹ and R² each independently represent an alkyl grouphaving 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms,an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy grouphaving 2 to 8 carbon atoms; A represents a 1,4-phenylene group or atrans-1,4-cyclohexylene group; l represents 1 or 2; and when 1 is 2, thetwo A may be the same or different from each other) and a compoundrepresented by general formula (II)

(In the formula, R³ represents an alkyl group having 1 to 8 carbonatoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy grouphaving 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbonatoms; R⁴ represents an alkyl group having 1 to 8 carbon atoms, analkenyl group having 4 to 8 carbon atoms, an alkoxy group having 1 to 8carbon atoms, or an alkenyloxy group having 3 to 8 carbon atoms; Brepresents a 1,4-phenylene group or a trans-1,4-cyclohexylene group; mrepresents 0, 1, or 2; and when m is 2, the two B may be the same ordifferent from each other).

Advantageous Effects of Invention

According to the present invention, the liquid crystal display devicehas a high response speed, suppresses ghosting, and has fewer drop marksresulting from the production process. Thus, the liquid crystal displaydevice can be effectively used as a display device for liquid crystalTVs and monitors.

According to the present invention, liquid crystal display devices canbe produced efficiently while suppressing occurrence of drop marks.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic perspective view showing an embodiment of a liquidcrystal display device according to the present invention.

FIG. 2 is a schematic plan view showing an example of a slit electrode(comb-shape electrode) used in the liquid crystal display deviceaccording to the present invention.

FIG. 3 is a diagram showing the definition of a pretilt angle in theliquid crystal display device according to the present invention.

DESCRIPTION OF EMBODIMENTS

Embodiments of a liquid crystal display device and a method forproducing the liquid crystal display device according to the presentinvention will now be described.

The embodiments are provided to specifically describe and promote betterunderstanding of the essence of the present invention and do not limitthe scope of the invention unless otherwise noted.

[Liquid Crystal Display Device]

A liquid crystal display device of the present invention includes aliquid crystal composition layer sandwiched between a pair of substratesand is based on the principle that the liquid crystal molecules in theliquid crystal composition layer work as an optical switch underapplication of voltage by Freedericksz transition. With regard to this,a known technology can be used.

Two substrates have electrodes for causing liquid crystals to undergoFreedericksz transition. In a common vertical alignment liquid crystaldisplay device, a technique of vertically applying charges between thetwo substrates is employed. In this case, one of the electrodes isconfigured as a common electrode and the other electrode is configuredas a pixel electrode. A typical embodiment that employs this techniqueis described below.

FIG. 1 is a schematic perspective view showing an embodiment of theliquid crystal display device according to the present invention.

A liquid crystal display device 10 includes a first substrate 11; asecond substrate 12; a liquid crystal composition layer 13 sandwichedbetween the first substrate 11 and the second substrate 12; a commonelectrode 14 formed on a surface of the first substrate 11, the surfacefacing the liquid crystal composition layer 13; a pixel electrode 15formed on a surface of the second substrate 12, the surface facing theliquid crystal composition layer 13; a vertical alignment film 16 formedon a surface of the common electrode 14, the surface facing the liquidcrystal composition layer 13; a vertical alignment film 17 formed on asurface of the pixel electrode 15, the surface facing the liquid crystalcomposition layer 13; and a color filter 18 interposed between the firstsubstrate 11 and the common electrode 14.

Glass substrates or plastic substrates are used as the first substrate11 and the second substrate 12.

Examples of the plastic substrate include substrates composed of a resinsuch as an acrylic resin, a methacrylic resin, polyethyleneterephthalate, polycarbonate, or a cyclic olefin resin.

The common electrode 14 is usually composed of a material, such asindium-doped tin oxide (ITO), that has transparency.

The pixel electrode 15 is usually composed of a material, such asindium-doped tin oxide (ITO), that has transparency.

The pixel electrode 15 formed on the second substrate 12 has a matrixshape. The pixel electrode 15 is controlled by drain electrodes ofactive elements such as TFT switching elements. The TFT switchingelements have gate lines which are address signal lines and source lineswhich are data lines arranged in a matrix. In this description, thestructure of the TFT switching elements is not illustrated in thedrawings.

In the case where a pixel is divided into a number of domains to tiltliquid crystal molecules in the pixel in several different directions inorder to improve the viewing angle characteristics, a pixel electrodethat has slits (portions where no electrode is formed) in a stripepattern or a V-shape pattern may be provided in the pixel.

FIG. 2 is a schematic plan view showing a typical geometry of a slitelectrode (comb-shape electrode) for dividing a pixel into four domains.Since this slit electrode has comb-tooth slits extending in fourdirections from the center of the pixel, the liquid crystal molecules inthe pixel that are vertically aligned relative to the substrate in theabsence of an applied voltage will have their directors tilting in fourdifferent directions toward horizontal alignment under application ofvoltage. As a result, the liquid crystal molecules in the pixel align inplural different directions and thus a significantly wide viewing anglecharacteristic is achieved.

Examples of the method for dividing a pixel include, in addition to themethod of forming slits in a pixel electrode, a method with whichstructures such as linear projections and the like are formed in a pixeland a method with which electrodes other than the pixel electrode andthe common electrode are formed. Although these methods can also be usedto align liquid crystal molecules in different directions, it ispreferable to use a slit electrode from the viewpoints of transmittanceand ease of manufacturing. A pixel electrode having slits has no powerto drive liquid crystal molecules in the absence of an applied voltageand thus a pretilt angle cannot be provided to the liquid crystalmolecules. However, when a slit electrode is used in combination with analignment film material used in the present invention, a pretilt rangecan be provided. Moreover, a wide viewing angle can be achieved when thealignment film material is used in combination with a slit electrodethat divides a pixel into domains.

In the present invention, having a pretilt angle refers to a state inwhich the director of liquid crystal molecules deviates slightly from adirection vertical to the substrate surface (the surface of the firstsubstrate 11 or the surface of the second substrate 12 adjacent to theliquid crystal composition layer 13) in the absence of an appliedvoltage.

Since the liquid crystal display device of the present invention is avertical alignment (VA)-type liquid crystal display device, the directorof the liquid crystal molecules is aligned substantially vertically tothe substrate surface in the absence of an applied voltage. In order tohave the liquid crystal molecules align vertically, a vertical alignmentfilm is usually used. Examples of the material constituting the verticalalignment film (vertical alignment film material) include polyimide,polyamide, and polysiloxane. Among these, polyimide is preferable.

The vertical alignment film material may include a mesogenic moiety butis preferably free of mesogenic moieties unlike in the polymerizablecompound described below. When the vertical alignment film materialcontains a mesogenic moiety, for example, ghosting caused by disturbanceof the molecular alignment may result from repeated voltage application.

When the vertical alignment film is to be composed of polyimide, apolyimide solution in which a mixture of tetracarboxylic dianhydride anda diisocyanate, polyamic acid, and polyimide are dissolved or dispersedin a solvent is preferably used. In this case, the polyimide content inthe polyimide solution is preferably 1 mass % or more and 10 mass % orless, more preferably 3 mass % or more and 5 mass % or less, and mostpreferably 10 mass % or less.

In contrast, when a polysiloxane-based vertical alignment film is to beused, a polysiloxane solution prepared by dissolving polysiloxaneproduced by heating a mixture of a silicon compound having an alkoxygroup, an alcohol derivative, and an oxalic acid derivative mixed atparticular ratios can be used.

In the liquid crystal display device of the present invention, thevertical alignment film formed of polyimide or the like contains apolymer formed by polymerization of a polymerizable compound having areactive group. This polymerizable compound helps fix the pretilt angleof the liquid crystal molecules. In other words, the directors of theliquid crystal molecules in the pixel can be made to tilt in differentdirections under application of voltage by using a slit electrode andthe like. However, even in a structure that uses a slit electrode, theliquid crystal molecules are substantially vertically aligned relativeto the substrate surface in the absence of an applied voltage and nopretilt angle is formed.

According to the PSA method described above, UV light or the like isapplied while applying a voltage between the electrodes to slightly tiltthe liquid crystal molecules so as to polymerize the reactive monomer inthe liquid crystal composition and to provide an appropriate pretiltangle.

In the liquid crystal display device of this invention, UV light or thelike is applied while applying a voltage between the electrodes toslightly tilt the liquid crystal molecules so as to provide a pretiltangle as with the PSA method. However, unlike the PSA method, nopolymerizable compound is contained in the liquid crystal composition.In the present invention, a polymerizable compound having a reactivegroup is added to the vertical alignment film material such as polyimideor the like in advance, the liquid crystal composition is sandwichedbetween the substrates, and then the polymerizable compound is curedunder application of voltage to provide pretilt angles. This isessentially different from the PSA method in that the phase separationof the polymerizable compound is not utilized.

In the present invention, substantially vertical refers to a state inwhich the director of vertically aligned liquid crystal molecules isslightly tilted from the vertical direction and has a pretilt angle.Assuming that the pretilt angle is 90° when the director is perfectlyvertical and the pretilt angle is 0° when the alignment is homogeneous(horizontal to the substrate surface), substantially vertical preferablyrefers to an angle of 89 to 85° and more preferably 89 to 87°.

The vertical alignment film that contains a polymer of a polymerizablecompound that has a reactive group is formed by an effect of thepolymerizable compound added to the vertical alignment film material.Presumably, the vertical alignment film and the polymerizable compoundare intricately entangled to form a type of a polymer alloy; however,its exact structure cannot be identified.

(Polymerizable Compound Having Reactive Group)

The polymerizable compound that has a reactive group is a compound thathas a polyimide skeleton as a main chain and a crosslinkable functionalgroup as a side chain. From the viewpoint of durability, thepolymerizable compound having a reactive group is preferably adifunctional, trifunctional, or higher functional polymerizable compoundhaving two or more reactive groups.

The reactive group of the polymerizable compound having a reactive groupis preferably a photopolymerizable substituent. In particular, thereactive group is preferably a photopolymerizable substituent since, inmaking a vertical alignment film by thermal polymerization by thermallypolymerizing the vertical alignment film material, the reaction of thepolymerizable compound having a reactive group can be suppressed.

The main chain of the polymerizable compound having a reactive group ispreferably a thermosetting polyimide or a soluble polyimide.

The polymerizable compound having a reactive group is specificallypreferably a polymerizable compound represented by general formula (V)below:

(In the formula, X¹ and X² each independently represent a hydrogen atomor a methyl group; Sp¹ and Sp² each independently represent a singlebond, an alkylene group having 1 to 8 carbon atoms, or —O—(CH₂)_(s)— (inthe formula, s represents an integer of 2 to 7 and the oxygen atom is tobond with an aromatic ring); U represents a linear or branchedpolyvalent alkylene group having 2 to 20 carbon atoms or a polyvalentcyclic substituent having 5 to 30 carbon atoms; an alkylene group in thepolyvalent alkylene group may be substituted with an oxygen atom as longas the oxygen atoms are not adjacent to each other, or may besubstituted with an alkyl group having 5 to 20 carbon atoms (an alkylenegroup in the group may be substituted with an oxygen atom as long as theoxygen atoms are not adjacent to each other) or a cyclic substituent;and k represents an integer of 1 to 5.).

In general formula (V) above, X¹ and X² each independently represent ahydrogen atom or a methyl group. If the reaction speed is important, ahydrogen atom is preferable. If reducing the amount of reaction residuesis important, a methyl group is preferable.

In general formula (V) above, Sp¹ and Sp² each independently represent asingle bond, an alkylene group having 1 to 8 carbon atoms, or—O—(CH₂)_(s)— (in the formula, s represents an integer of 2 to 7 and theoxygen atom is to bond with an aromatic ring). However, the carbon chainis preferably not long. A single bond or an alkylene group having 1 to 5carbon atoms is preferred. A single bond or an alkylene group having 1to 3 carbon atoms is more preferred. When Sp¹ and Sp² each represent—O—(CH₂)_(s)—, s is preferably 1 to 5 and more preferably 1 to 3. Atleast one of Sp¹ and Sp² is preferably a single bond. More preferably,both Sp¹ and Sp² are a single bond.

In general formula (V) above, U represents a linear or branchedpolyvalent alkylene group having 2 to 20 carbon atoms or a multivalentcyclic substituent having 5 to 30 carbon atoms. An alkylene groups inthe polyvalent alkylene group may be substituted with an oxygen atom aslong as the oxygen atoms are not adjacent to each other, or may besubstituted with an alkyl group having 5 to 20 carbon atoms (an alkylenegroup in the group may be substituted with an oxygen atom as long as theoxygen atoms are not adjacent to each other) or a cyclic substituent.The number of cyclic substituent is preferably 2 or more.

In general formula (V) above, U specifically preferably represents anyone of formulae (Va-1) to (Va-5) below, more preferably any one offormulae (Va-1) to (Va-3) below, and most preferably formula (Va-1).

(In the formulae, each end is bonded to Sp¹ or Sp².)

When U has a cyclic structure, at least one of Sp¹ and Sp² preferablyrepresents a single bond. Preferably, both represent a single bond.

In general formula (V) above, k represents an integer of 1 to 5. Adifunctional compound having k representing 1 or a trifunctionalcompound having k representing 2 is preferable, and a difunctionalcompound is more preferable.

The compound represented by general formula (V) above is specificallypreferably a compound represented by general formula (Vb) below:

(In the formula, X¹ and X² each independently represent a hydrogen atomor a methyl group; Sp¹ and Sp² each independently represent a singlebond, an alkylene group having 1 to 8 carbon atoms, or —O—(CH₂)_(s)— (inthe formula, s represents an integer of 2 to 7 and the oxygen atom is tobond to an aromatic ring); Z¹ represents —OCH₂—, —CH₂O—, —COO—, —OCO—,—CF₂O—, —OCF₂—, —CH₂CH₂—, —CF₂CF₂—, —CH═CH—COO—, —CH═CH—OCO—,—COO—CH═CH—, —OCO—CH═CH—, —COO—CH₂CH₂—, —OCO—CH₂CH₂—, —CH₂CH₂—COO—,—CH₂CH₂—OCO—, —COO—CH₂—, —OCO—CH₂—, —CH₂—COO—, —CH₂—OCO—, —CY¹═CY²—,—C≡C—, or a single bond; C represents a 1,4-phenylene group, atrans-1,4-cyclohexylene group, or a single bond; and all of the1,4-phenylene groups in the formula may have any hydrogen atomsubstituted with a fluorine atom.).

In general formula (Vb) above, X¹ and X² each independently represent ahydrogen atom or a methyl group. However, a diacrylate derivative inwhich X¹ and X² each represent a hydrogen atom or a dimethacrylatederivative in which X¹ and X² each represent a methyl group ispreferred. A compound in which one of X¹ and X² represents a hydrogenatom and the other represents a methyl group is also preferable.Regarding the polymerization speed of these compounds, the diacrylatederivative is the highest, the dimethacrylate derivative is the lowest,and an unsymmetrical compound is intermediate. A preferable compound isto be selected according to the usage. For a PSA liquid crystal displaydevice, a dimethacrylate derivative is particularly preferable.

In general formula (Vb) above, Sp¹ and Sp² each independently representa single bond, an alkylene group having 1 to 8 carbon atoms, or—O—(CH₂)_(s)—. For a PSA liquid crystal display device, at least one ofSp¹ and Sp² is preferably a single bond. A compound in which both Sp¹and Sp² represent a single bond or a compound in which one of Sp¹ andSp² is a single bond and the other is an alkylene group having 1 to 8carbon atoms or —O—(CH₂)_(s)— is preferable. In this case, an alkylenegroup having 1 to 4 carbon atoms is preferable and s is preferably 1 to4.

In general formula (Vb) above, Z¹ represents —OCH₂—, —CH₂O—, —COO—,—OCO—, —CF₂O—, —OCF₂—, —CH₂CH₂—, —CF₂CF₂—, —CH═CH—COO—, —CH═CH—OCO—,—COO—CH═CH—, —OCO—CH═CH—, —COO—CH₂CH₂—, —OCO—CH₂CH₂—, —CH₂CH₂—COO—,—CH₂CH₂—OCO—, —COO—CH₂—, —OCO—CH₂—, —CH₂—OCO—, —CH₂—OCO—, —CY¹═CY²—,—C≡C—, or a single bond. Z¹ is preferably —OCH₂—, —CH₂O—, —COO—, —OCO—,—CF₂O—, —OCF₂—, —CH₂CH₂—, —CF₂CF₂—, or a single bond, more preferably—COO—, —OCO—, or a single bond, and most preferably a single bond.

In general formula (Vb) above, C may be a 1,4-phenylene group that mayhave any hydrogen atom substituted with a fluorine atom, atrans-1,4-cyclohexylene group, or a single bond but is preferably a1,4-phenylene group or a single bond.

When C represents a cyclic structure and not a single bond, Z¹ ispreferably a linking group other than a single bond. When C is a singlebond, Z¹ is preferably a single bond.

In sum, in general formula (Vb) above, the case in which C represents asingle bond and a cyclic structure is constituted by two rings ispreferred. The polymerizable compound having a cyclic structure ispreferably any one of compounds represented by general formulae (V-1) to(V-6) below, more preferably any one of compounds represented by generalformulae (V-1) to (V-4) below, and most preferably a compoundrepresented by general formula (V-2) below.

(Liquid Crystal Composition)

The liquid crystal composition of the present invention preferablycontains 30 to 65 mass %, more preferably 30 to 50 mass %, yet morepreferably 35 to 45 mass %, and most preferably 38 to 42 mass % of acompound represented by general formula (I) below as a first component.

(In the formula, R¹ and R² each independently represent an alkyl grouphaving 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms,an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy grouphaving 2 to 8 carbon atoms; A represents a 1,4-phenylene group or atrans-1,4-cyclohexylene group; l represents 1 or 2; and when l is 2, thetwo A may be the same or different from each other.)

In general formula (I) above, R¹ and R² each independently represent analkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or analkenyloxy group having 2 to 8 carbon atoms.

R¹ and R² preferably each represent an alkyl group having 1 to 5 carbonatoms, an alkenyl group having 2 to 5 carbon atoms, an alkoxy grouphaving 1 to 5 carbon atoms, or an alkenyloxy group having 2 to 5 carbonatoms.

R¹ and R² more preferably each represent an alkyl group having 2 to 5carbon atoms, an alkenyl group having 2 to 4 carbon atoms, an alkoxygroup having 1 to 4 carbon atoms, or an alkenyloxy group having 2 to 4carbon atoms.

R¹ and R² most preferably each represent an alkyl group having 2 to 5carbon atoms or an alkenyl group having 2 to 4 carbon atoms.

When R¹ represents an alkyl group, an alkyl group having 1, 3, or 5carbon atoms is particularly preferable. When R¹ represents an alkenylgroup, the following structures are preferable.

(In the formulae, the end on the right-hand side bonds with the cyclicstructure.)

Of the above-described structures, a vinyl group or a 1-propenyl groupwhich is an alkenyl group having 2 or 3 carbon atoms is particularlypreferable.

In general formula (I) above, R¹ and R² may be the same or differentfrom each other but are preferably different from each other. When bothR¹ and R² are an alkyl group, they are preferably alkyl groups having 1,3, or 5 carbon atoms with numbers of carbon atoms different from eachother.

The content of the compound represented by general formula (I) above inwhich at least one substituent selected from R¹ and R² is an alkyl grouphaving 3 to 5 carbon atoms is preferably 50 mass % or more, morepreferably 70 mass % or more, and most preferably 80 mass % or more ofthe compound represented by general formula (I) above.

The content of the compound represented by general formula (I) above inwhich at least one substituent selected from R¹ and R² is an alkyl grouphaving 3 carbon atoms is preferably 50 mass % or more, more preferably70 mass % or more, yet more preferably 80 mass % or more, and mostpreferably 100% of the compound represented by general formula (I)above.

In general formula (I) above, A represents a 1,4-phenylene group or atrans-1,4-cyclohexylene group but preferably represents atrans-1,4-cyclohexylene group. The content of the compound representedby general formula (I) in which A represents a trans-1,4-cyclohexylenegroup is preferably 50 mass % or more, more preferably 70 mass % ormore, and most preferably 80 mass % or more of the compound representedby general formula (I).

The compound represented by general formula (I) is preferably any one ofcompounds represented by general formulae (Ia) to (Ik) below:

(In the formulae, R¹ and R² each independently represent an alkyl grouphaving 1 to 5 carbon atoms or an alkoxy group having 1 to 5 carbon atomsbut the embodiments similar to R¹ and R² in general formula (I) arepreferred.)

Among general formulae (Ia) to (Ik) above, general formulae (Ia), (Ib),and (Ig) are preferable and general formulae (Ia) and (Ig) are morepreferable. In order to improve the response speed, reduce ghosting, andsuppress drop marks in a well balanced manner, general formula (Ia) isparticularly preferable. When the response speed is important, generalformula (Ib) is also preferable. When the response speed is critical,general formulae (Ib), (Ie), (If), and (Ih) are preferable. Thedialkenyl compounds represented by general formulae (Ie) and (If) areparticularly preferable when the response speed is important.

Based on these points, the content of the compounds represented bygeneral formulae (Ia) and (Ig) is preferably 50 mass % or more, morepreferably 70 mass % or more, yet more preferably 80 mass % or more, andmost preferably 100 mass % of the compound represented by generalformula (I) above. The content of the compound represented by generalformula (Ia) above is preferably 50 mass % or more, more preferably 70mass % or more, and most preferably 80 mass % or more of the compoundrepresented by general formula (I).

The liquid crystal composition of the present invention preferablycontains 5 to 20 mass %, more preferably 10 to 15 mass %, and mostpreferably 12 to 14 mass % of a compound represented by general formula(II-1) below as a second component.

(In the formula, R³ represents an alkyl group having 1 to 8 carbonatoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy grouphaving 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbonatoms; and R⁴ represents an alkyl group having 1 to 8 carbon atoms, analkenyl group having 4 to 8 carbon atoms, an alkoxy group having 1 to 8carbon atoms, or an alkenyloxy group having 3 to 8 carbon atoms.)

In general formula (II-1) above, R³ represents an alkyl group having 1to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, analkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 2to 8 carbon atoms.

R³ preferably represents an alkyl group having 1 to 5 carbon atoms or analkenyl group having 2 to 5 carbon atoms.

R³ more preferably represents an alkyl group having 2 to 5 carbon atomsor an alkenyl group having 2 to 4 carbon atoms.

R³ yet more preferably represents an alkyl group having 3 to 5 carbonatoms or an alkenyl group having 2 carbon atoms.

R³ most preferably represents an alkyl group having 3 carbon atoms.

In general formula (II-1) above, R⁴ represents an alkyl group having 1to 8 carbon atoms, an alkenyl group having 4 to 8 carbon atoms, analkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 3to 8 carbon atoms.

R⁴ preferably represents an alkyl group having 1 to 5 carbon atoms or analkoxy group having 1 to 5 carbon atoms.

R⁴ more preferably represents an alkyl group having 1 to 3 carbon atomsor an alkoxy group having 1 to 3 carbon atoms.

R⁴ yet more preferably represents an alkyl group having 3 carbon atomsor an alkoxy group having 2 carbon atoms.

R⁴ most preferably represents an alkoxy group having 2 carbon atoms.

The compound represented by general formula (II-1) above is specificallypreferably a compound represented by general formula (II-1a) or (II-1b)below:

(In the formulae, R³ represents an alkyl group having 1 to 5 carbonatoms or an alkenyl group having 2 to 5 carbon atoms; and R^(4a)represents an alkyl group having 1 to 5 carbon atoms.)

In general formula (II-1a), R³ is preferably similar to embodiments forgeneral formula (II-1) described above.

In general formula (II-Ia) above, R^(4a) is preferably an alkyl grouphaving 1 to 3 carbon atoms, more preferably an alkyl group having 1 or 2carbon atoms, and most preferably an alkyl group having 2 carbon atoms.

In general formula (II-1b) above, R³ is preferably similar toembodiments for general formula (II-1) described above.

In general formula (II-Ib) above, R^(4a) is preferably an alkyl grouphaving 1 to 3 carbon atoms, more preferably an alkyl group having 1 or 3carbon atoms, and most preferably an alkyl group having 3 carbon atoms.

Of general formulae (II-1a) and (II-1b), general formula (II-1a) ispreferable in order to increase the absolute value of the dielectricanisotropy.

The liquid crystal composition of the present invention preferablycontains 25 to 45 mass %, more preferably 30 to 40 mass %, and mostpreferably 31 to 36 mass % of a compound represented by general formula(II-2) below as a third component.

(In the formula, R³ represents an alkyl group having 1 to 8 carbonatoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy grouphaving 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbonatoms; R⁴ represents an alkyl group having 1 to 8 carbon atoms, analkenyl group having 4 to 8 carbon atoms, an alkoxy group having 1 to 8carbon atoms, or an alkenyloxy group having 3 to 8 carbon atoms; Brepresents a 1,4-phenylene group or a trans-1,4-cyclohexylene group; mrepresents 0, 1, or 2.)

In general formula (II-2) above, R⁵ represents an alkyl group having 1to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, analkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 2to 8 carbon atoms.

R⁵ preferably represents an alkyl group having 1 to 5 carbon atoms or analkenyl group having 2 to 5 carbon atoms.

R⁵ more preferably represents an alkyl group having 2 to 5 carbon atomsor an alkenyl group having 2 to 4 carbon atoms.

R⁵ more yet preferably represents an alkyl group having 3 to 5 carbonatoms or an alkenyl group having 2 carbon atoms.

R⁵ most preferably represents an alkyl group having 3 carbon atoms.

In general formula (II-2), R⁶ represents an alkyl group having 1 to 8carbon atoms, an alkenyl group having 4 to 8 carbon atoms, an alkoxygroup having 1 to 8 carbon atoms, or an alkenyloxy group having 3 to 8carbon atoms.

R⁶ preferably represents an alkyl group having 1 to 5 carbon atoms or analkoxy group having 1 to 5 carbon atoms.

R⁶ more preferably represents an alkyl group having 1 to 3 carbon atomsor an alkoxy group having 1 to 3 carbon atoms.

R⁶ yet more preferably represents an alkyl group having 3 carbon atomsor an alkoxy group having 2 carbon atoms.

R⁶ most preferably represents an alkoxy group having 2 carbon atoms.

In general formula (II-2), B represents a 1,4-phenylene group which maybe substituted with fluorine or a trans-1,4-cyclohexylene group. Bpreferably represents an unsubstituted 1,4-phenylene group or atrans-1,4-cyclohexylene group and more preferably atrans-1,4-cyclohexylene group.

The compound represented by general formula (II-2) above is preferably acompound represented by any one of general formulae (II-2a) to (II-2d)below.

(In the formulae, R⁵ represents an alkyl group having 1 to 5 carbonatoms or an alkenyl group having 2 to 5 carbon atoms; R^(6a) representsan alkyl group having 1 to 5 carbon atoms; and R⁵ and R^(6a) arepreferably similar to embodiments of R⁵ and R⁶ in general formula(II-2).)

In general formulae (II-2a) and (II-2b), R⁵ is preferably similar to theembodiment in general formula (II-2).

In general formulae (II-2a) and (II-2b), R^(6a) is preferably an alkylgroup having 1 to 3 carbon atoms, more preferably an alkyl group having1 or 2 carbon atoms, and most preferably an alkyl group having 2 carbonatoms.

In general formulae (II-2c) and (II-2d), R⁵ is preferably similar to theembodiment in general formula (II-2).

In general formulae (II-2c) and (II-2d), R^(6a) is preferably an alkylgroup having 1 to 3 carbon atoms, more preferably an alkyl group having1 or 3 carbon atoms, and most preferably an alkyl group having 3 carbonatoms.

Of general formulae (II-2a) and (II-2b) above, general formula (II-2a)is preferred in order to increase the absolute value of the dielectricanisotropy. For a composition with a high Δn, general formula (II-2b) ispreferred.

The liquid crystal composition of the present invention preferablycontains 5 to 20 mass %, more preferably 8 to 15 mass %, and mostpreferably 10 to 13 mass % of a compound represented by general formula(III) below as a fourth component.

(In the formula, R⁷ and R⁸ each independently represent an alkyl grouphaving 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms,an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy grouphaving 2 to 8 carbon atoms; Y¹ and Y² each independently represent ahydrogen atom or a fluorine atom; D, E, and F each independentlyrepresent a 1,4-phenylene group or trans-1,4-cyclohexylene; Z²represents a single bond, —OCH₂—, —OCO—, —CH₂O—, or —COO—; and nrepresents 0 or 1.)

In general formula (III), R⁷ represents an alkyl group having 1 to 8carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxygroup having 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8carbon atoms.

When D represents trans-1,4-cyclohexylene, R⁷ preferably represents analkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 5carbon atoms, more preferably represents an alkyl group having 2 to 5carbon atoms or an alkenyl group having 2 to 4 carbon atoms, yet morepreferably represents an alkyl group having 3 to 5 carbon atoms or analkenyl group having 2 carbon atoms, and most preferably represents analkyl group having 3 carbon atoms.

When D represents a 1,4-phenylene group which may be substituted withfluorine, R⁷ preferably represents an alkyl group having 1 to 5 carbonatoms or an alkenyl group having 4 or 5 carbon atoms, more preferablyrepresents an alkyl group having 2 to 5 carbon atoms or an alkenyl grouphaving 4 carbon atoms, and most preferably represents an alkyl grouphaving 2 to 4 carbon atoms.

In general formula (III) above, R⁸ represents an alkyl group having 1 to8 carbon atoms, an alkenyl group having 4 to 8 carbon atoms, an alkoxygroup having 1 to 8 carbon atoms, or an alkenyloxy group having 3 to 8carbon atoms.

When F represents trans-1,4-cyclohexylene, R⁸ preferably represents analkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 5carbon atoms, more preferably represents an alkyl group having 2 to 5carbon atoms or an alkenyl group having 2 to 4 carbon atoms, yet morepreferably represents an alkyl group having 3 to 5 carbon atoms or analkenyl group having 2 carbon atoms, and most preferably represents analkyl group having 3 carbon atoms.

When F represents a 1,4-phenylene group which may be substituted withfluorine, R⁸ preferably represents an alkyl group having 1 to 5 carbonatoms or an alkenyl group having 4 or 5 carbon atoms, more preferablyrepresents an alkyl group having 2 to 5 carbon atoms or an alkenyl grouphaving 4 carbon atoms, and most preferably represents an alkyl grouphaving 2 to 4 carbon atoms.

When R⁷ and R⁸ each represent an alkenyl group and D or F bonded theretorepresents a 1,4-phenylene group which may be substituted with fluorinein general formula (III), the alkenyl group having 4 or 5 carbon atomspreferably has a structure represented by a formula below:

(In the formulae, the end on the right-hand side is bonded to the cyclicstructure.)

In this case also, an alkenyl group having 4 carbon atoms is morepreferable.

In general formula (III) above, Y¹ and Y² each independently represent ahydrogen atom or a fluorine atom. Preferably, at least one of Y¹ and Y²represents a fluorine atom. When the absolute value of the dielectricanisotropy is important, both Y¹ and Y² preferably represent a fluorineatom.

In general formula (III) above, D, E, and F each independently representa 1,4-phenylene group, which may be substituted with fluorine, ortrans-1,4-cyclohexylene but preferably represent an unsubstituted1,4-phenylene group or trans-1,4-cyclohexylene.

In general formula (III) above, Z² represents a single bond, —OCH₂—,—OCO—, —CH₂O—, or —COO—. Z² preferably represents a single bond, —CH₂O—,or —COO— and more preferably represents a single bond.

In general formula (III), n represents 0 or 1. When Z² represents asubstituent and not a single bond, n preferably represents 0.

The compound represented by general formula (III) with n representing 0is specifically preferably a compound represented by any one of generalformulae (III-1a) to (III-1h) below.

(In formulae, R⁷ and R⁸ each independently represent an alkyl grouphaving 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms,or an alkoxy group having 1 to 5 carbon atoms but are preferably similarto the embodiments of R⁷ and R⁸ in general formula (III).)

The compound represented by general formula (III) with n representing 1is specifically preferably a compound represented by any one of generalformulae (III-2a) to (III-2l) below.

(In formulae, R⁷ and R⁸ each independently represent an alkyl grouphaving 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms,or an alkoxy group having 1 to 5 carbon atoms but are preferably similarto the embodiments of R⁷ and R⁸ in general formula (III).)

The liquid crystal composition of the present invention is constitutedby a combination of compounds represented by general formulae (I) to(III) above. The contents of the respective compounds contained incombination are preferably as follows.

The compounds represented by general formulae (II-1) and (II-2) are eacha compound having a negative dielectric anisotropy with a relativelylarge absolute value. The total content of these compounds in the liquidcrystal composition is preferably 30 to 65 mass %, more preferably 40 to55 mass %, and most preferably 43 to 50 mass %.

The compound represented by general formula (III) above may have apositive dielectric anisotropy or a negative dielectric anisotropy. Whena compound represented by general formula (III) with a negativedielectric anisotropy having an absolute value of 0.3 or more is used,the total content of the compounds represented by general formulae(II-1), (II-2), and (III) is preferably 35 to 70 mass %, more preferably45 to 65 mass %, and most preferably 50 to 60 mass %.

The liquid crystal composition of the present invention preferablycontains 30 to 50 mass % of a compound represented by general formula(I) above, and a total of 35 to 70 mass % of compounds represented bygeneral formulae (II-1), (II-2), and (III).

More preferably, the liquid crystal composition contains 35 to 45 mass %of a compound represented by general formula (I) above, and a total of45 to 65 mass % of compounds represented by general formulae (II-1),(II-2), and (III).

Yet more preferably, the liquid crystal composition contains 38 to 42mass % of a compound represented by general formula (I) above, a totalof 50 to 60 mass % of compounds represented by general formulae (II-1),(II-2), and (III).

The total content of the compounds represented by general formulae (I),(II-1), (II-2), and (III) is preferably 80 to 100 mass %, morepreferably 90 to 100 mass %, and most preferably 95 to 100 mass %relative to the entire liquid crystal composition.

The liquid crystal composition of the present invention can be used in awide range of the nematic phase-isotropic liquid phase transitiontemperature (T_(ni)). The nematic phase-isotropic liquid phasetransition temperature (T_(ni)) is preferably 60 to 120° C., morepreferably 70 to 100° C., and most preferably 70 to 85° C.

The dielectric anisotropy of the liquid crystal composition of thepresent invention is preferably −2.0 to −6.0, more preferably −2.5 to−5.0, and most preferably −2.5 to −3.5 at 25° C.

The refractive index anisotropy of the liquid crystal composition of thepresent invention is preferably 0.08 to 0.13 and more preferably 0.09 to0.12 at 25° C. To be more specific, when the cell gap is small, therefractive index anisotropy of the liquid crystal composition of thepresent invention is preferably 0.10 to 0.12 at 25° C. When the cell gapis large, the refractive index anisotropy of the liquid crystalcomposition of the present invention is preferably 0.08 to 0.10 at 25°C.

[Method for Producing Liquid Crystal Display Device]

Next, a method for producing a liquid crystal display device of thepresent invention is described with reference to FIG. 1.

An alignment material that contains a polymerizable compound having areactive group and a vertical alignment material is applied to a surfaceof the first substrate 11 on which the common electrode 14 is formed andto a surface of the second substrate 12 on which the pixel electrode 15is formed and heated to form the vertical alignment films 16 and 17.

In this step, first, an alignment material that contains a polymercompound precursor (polymerizable compound) that forms a first polymercompound and a polymerizable compound such as a compound represented bygeneral formula (V) or a photo-polymerizable or photo-crosslinkablecompound is prepared.

When the first polymer compound is polyimide, the polymer compoundprecursor is, for example, a polyimide solution in which a mixture oftetracarboxylic dianhydride and a diisocyanate, polyamic acid, andpolyimide are dissolved or dispersed in a solvent. The polyimide contentin the polyimide solution is preferably 1 mass % or more and 10 mass %or less and more preferably 3 mass % or more and 5 mass % or less.

When the first polymer compound is polysiloxane, the polymer compoundprecursor is, for example, a polysiloxane solution prepared bydissolving, in a solvent, polysiloxane produced by heating a mixture ofa silicon compound having an alkoxy group, a silicon compound having ahalogenated alkoxy group, an alcohol, and an oxalic acid derivativemixed at particular ratios.

If needed, a photo-crosslinkable compound, a photopolymerizationinitiator, a solvent, and the like may be added to the alignmentmaterial.

After the alignment material is prepared, the alignment material isapplied to or printed on each of the first substrate 11 and the secondsubstrate 12 so as to cover the common electrode 14, and the pixelelectrode 15 and slit portions (not shown in the drawing), and thensubjected to a treatment such as heating. As a result, the polymercompound precursor contained in the applied or printed alignmentmaterial is polymerized and cured to form a first polymer compound andvertical alignment films 16 and 17 that contain the first polymercompound and the polymerizable compound are formed.

In the case where a heat treatment is to be performed, the temperatureis preferably 80° C. or higher and more preferably in the range of 150to 200° C.

The alignment control portion that contains the first polymer compoundis formed at this stage. A treatment such as rubbing may be conductedafter this as needed.

Next, the first substrate 11 and the second substrate 12 are stacked andthe liquid crystal composition layer 13 containing liquid crystalmolecules is sealed in between the substrates.

In particular, spacer projections, such as plastic beads for example,for securing the cell gap are scattered onto the surface of one of thefirst substrate 11 and the second substrate 12 on which the verticalalignment film 16 or 17 is formed and a sealing portion is printed byscreen printing using an epoxy adhesive or the like.

Then the first substrate 11 and the second substrate 12 are bonded toeach other with the spacer projections and the sealing portiontherebetween so that the vertical alignment films 16 and 17 face eachother and then a liquid crystal composition containing liquid crystalmolecules is poured.

Then the sealing portion is cured by heating or the like to seal in theliquid crystal composition between the first substrate 11 and the secondsubstrate 12.

Next, voltage is applied between the common electrode 14 and the pixelelectrode 15 by using voltage application means. For example, a voltageof 5 to 30 (V) is applied. As a result, an electric field is generatedin a direction that forms a particular angle with the surface of thefirst substrate 11 adjacent to the liquid crystal composition layer 13(the surface facing the liquid crystal composition layer 13) and thesurface of the second substrate 12 adjacent to the liquid crystalcomposition layer 13 (surface facing the liquid crystal compositionlayer 13). Thus liquid crystal molecules 19 tilt in a particulardirection from a normal direction of the first substrate 11 and thesecond substrate 12. At this stage, the tilt angle of the liquid crystalmolecules 19 is substantially equal to the pretilt angle provided to theliquid crystal molecules 19 in the step described below. Accordingly,the magnitude of the pretilt θ of the liquid crystal molecules 19 can becontrolled by appropriately adjusting the magnitude of the voltage(refer to FIG. 3).

Then ultraviolet light UV is applied to the liquid crystal compositionlayer 13 from the outer side of the first substrate 11, for example,while applying the voltage so as to polymerize the polymerizablecompound in the vertical alignment films 16 and 17 and form a secondpolymer compound.

In this case, the intensity of the ultraviolet light UV applied may beconstant or varied. In the case where the intensity of irradiation is tobe varied, the irradiation time at the respective strength may be any.When irradiation is conducted in two or more stages, the irradiationintensity of the second stage and onward is preferably smaller than theirradiation intensity of the first stage. The total irradiation time ofthe second stage and onward is preferably longer than the irradiationtime of the first stage. The total irradiation energy quantity of thesecond stage and onward is also preferably higher than that of the firststage. When the irradiation intensity is to be discontinuously varied,the average irradiation intensity in the first half of the entireirradiation time is preferably larger than the average irradiationintensity in the second half. Preferably, the intensity immediatelyafter start of irradiation is the highest. More preferably, theirradiation intensity keeps decreasing to a particular value with thepassage of the irradiation time. The ultraviolet light UV intensity inthis case is preferably 2 mW/cm⁻² to 100 mW/cm⁻². More preferably, thehighest irradiation intensity in the first stage of multi-stageirradiation or in all irradiation stages in which the irradiationintensity is discontinuously varied is 10 mW/cm⁻² to 100 mW/cm⁻²; andthe lowest irradiation intensity in the second stage and onward ofmulti-stage irradiation or in discontinuously varying the irradiationintensity is 2 mW/cm⁻² to 50 mW/cm⁻². The total irradiation energyquantity is preferably 10 J to 300 J, more preferably 50 J to 250 J, andmost preferably 100 J to 250 J.

In such a case, the applied voltage may be AC or DC.

As a result, alignment regulating portions (not shown in the drawings)fixed to the alignment control portions of the vertical alignment film16 and 17 and containing the second polymer compound are formed. Thealignment regulating portions provide a pretilt θ to the liquid crystalmolecules 19 located near the interfaces between the liquid crystalcomposition layer 13 and the vertical alignment film 16 and between theliquid crystal composition layer 13 and the vertical alignment film 17in a non-operating state. Although ultraviolet light UV is applied fromthe outer side of the first substrate 11, it may be applied from theouter side of the second substrate 12 or from both the outer side of thefirst substrate 11 and the outer side of the second substrate 12.

As described above, in the liquid crystal display device of the presentinvention, the liquid crystal molecules 19 in the liquid crystalcomposition layer 13 have a particular pretilt θ. Thus, compared to aliquid crystal display device not subjected to a pretilt treatment and aliquid crystal display apparatus that includes such a liquid crystaldisplay device, the speed of response to the driving voltage can besignificantly improved.

In the liquid crystal display device of the present invention, thepolymer compound precursor constituting the vertical alignment films 16and 17 is preferably a polyimide precursor that is not sensitive tolight.

The content of the polymerizable compound, in particular, a compoundrepresented by general formula (V) above is preferably 0.5 to 4 mass %and more preferably 1 to 2 mass % in the polymer compound precursor.

EXAMPLES

The present invention will now be described in more specific detailsthrough Examples and Comparative Examples. It should be understood thatthe present invention is not limited to Examples described below. Forthe compositions of Examples and Comparative Examples, “%” means “mass%”.

In Examples and Comparative Examples below, T_(ni), Δn, Δ∈, η, and γ₁are defined as follows:

T_(ni): Nematic phase-isotropic liquid phase transition temperature (°C.)

Δn: Refractive index anisotropy at 25° C.

Δ∈: Dielectric anisotropy at 25° C.

η: Rotational viscosity at 20° C. (mPa·s)

γ₁: Rotational viscosity at 25° C. (mPa·s)

Liquid crystal display devices of Examples and Comparative Examplesbelow were evaluated by the following methods in terms of ghosting anddrop marks.

(Ghosting)

A particular fixed pattern was displayed in a display area for 1000hours and then an image is evenly displayed in all parts of the screenduring which the level of the afterimage of the fixed pattern wasobserved with naked eye. The ghosting level of the liquid crystaldisplay device was evaluated in four grades as described below:

AA: No afterimage.

A: Afterimage was observed slightly but was at an acceptable level.

B: Afterimage was observed and was at an unacceptable level.

C: Afterimage was observed and was far from the acceptable level.

(Drop Marks)

Drop marks that appeared white when black was displayed in all parts ofthe screen were observed with naked eye and the drop marks of the liquidcrystal display device were evaluated in four grades below:

AA: No afterimage.

A: Afterimage was observed slightly but was at an acceptable level.

B: Afterimage was observed and was at an unacceptable level.

C: Afterimage was observed and was far from the acceptable level.

In Examples, following abbreviations were used in describing compounds.

(Side Chain)

n represents —C_(n)H_(2n+1) (linear alkyl group with n carbon atoms).

On represents —OC_(n)H_(2n+1) (linear alkoxy group with n carbon atoms).

(Cyclic Structure)

Example 1

A first substrate (common electrode substrate) that has a transparentelectrode layer constituted by a transparent common electrode and acolor filter layer and a second substrate (pixel electrode substrate)having a pixel electrode layer that includes transparent pixelelectrodes driven by active elements were made.

Each pixel electrode of the pixel electrode substrate was made byetching ITO so that slits having no electrodes were formed in the pixelelectrode to align liquid crystal molecules in different directions.

A vertical alignment film material that contains a polyimide precursorand a polymerizable compound having a reactive group was applied to eachof the common electrode substrate and the pixel electrode substrate by aspin coating method. The applied films were heated at 200° C. to curethe polyimide precursor in the vertical alignment film material and forma 100 nm vertical alignment film on a surface of each substrate. At thisstage, the polymerizable compound having a reactive group contained inthe vertical alignment film was not yet cured.

An N-methyl-2-pyrrolidone solution containing 3% of a polyimidederivative represented by formula below and 3% of a polymerizablecompound having a reactive group represented by formula (V-2) below wasused as the vertical alignment film forming material.

A liquid crystal composition that contains compounds represented bychemical formulae below was sandwiched between the common electrodesubstrate and the pixel electrode substrate each with a verticalalignment film formed thereon. Then the sealing material was cured toform a liquid crystal composition layer. During this step, a spacerhaving a thickness of 4 μm was used to adjust the thickness of theliquid crystal composition layer to 4 μm.

In the chemical formulae shown below, compounds belonging to group (I)are compounds represented by general formula (I) above and compoundsbelonging to group (II) are compounds represented by general formula(II) above.

The liquid crystal display device obtained was irradiated withultraviolet light while applying a square AC field to cure thepolymerizable compound having a reactive group. UIS-S2511RZ produced byUshio Inc., and a UV lamp USH-250BY produced by Ushio Inc., were used asthe irradiators. The liquid crystal display device was irradiated withultraviolet light at 20 mW for 10 minutes to obtain a liquid crystaldisplay device of Example 1. As a result of this step, a verticalalignment film containing a polymer of a polymerizable compound having apolyimide skeleton as a main chain and a crosslinkable functional groupas a side chain was formed and a pretilt angle was provided to liquidcrystal molecules in the liquid crystal composition layer.

The pretilt angle is defined as shown in FIG. 3. If the molecules arealigned perfectly vertically, the pretilt angle (θ) is 90°. When apretilt angle is provided, the pretilt angle (θ) is smaller than 90°.

The liquid crystal display device of Example 1 has pretilt angles infour different directions in four domains, respectively, formed alongthe slits of the pixel electrode shown in FIG. 2. The pretilt angleswere retained after curing of the polymerizable compound even when theAC field was turned off. The pretilt angle retained was 87°.

The liquid crystal display device of Example 1 obtained as suchexhibited good response speed, suppressed drop marks, and exhibited goodghosting resistance as shown in Table 1.

TABLE 1 T_(NI)/° C. 81.0 Δn 0.103 n₀ 1.483 ε_(//) 3.3 ε_(⊥) 6.2 Δε −2.9η/mPa · s 20.3 γ₁/mPa · s 112 γ₁/Δn² × 10⁻² 104 Drop mark evaluation AAGhosting evaluation AA Response speed/ms 8.5

Comparative Example 1

A liquid crystal composition containing compounds represented bychemical formulae below was prepared and a liquid crystal display deviceof Comparative Example 1 was obtained as in Example 1 except that thisliquid crystal composition was used.

The liquid crystal display device of Comparative Example 1 was evaluatedin terms of ghosting and drop marks as in Example 1. The results areshown in Table 2.

The results show that the liquid crystal composition prepared inComparative Example 1 was inferior to the liquid crystal compositionprepared in Example 1. The liquid crystal composition prepared inComparative Example 1 exhibited a lower response speed than the liquidcrystal composition prepared in Example 1.

TABLE 2 T_(NI)/° C. 80.2 Δn 0.104 n₀ 1.481 ε_(//) 3.1 ε_(⊥) 6.0 Δε −3.0η/mPa · s 19.6 γ₁/mPa · s 143 γ₁/Δn² × 10⁻² 131 Drop mark evaluation CGhosting evaluation C Response speed/ms 10.8

Comparative Example 2

A liquid crystal composition having a composition shown in Table 3 wasprepared and a liquid crystal display device of Comparative Example 2was obtained as in Example 1 except that this liquid crystal compositionwas used.

TABLE 3 T_(NI)/° C. 80.2 Δn 0.103 n₀ 1.479 ε_(//) 3.1 ε_(⊥) 6.2 Δε −3.0η/mPa · s 18.5 γ₁/mPa · s 132 γ₁/Δn² × 10⁻² 125 3CyPh5O2 9% 3CyPh5O2 9%2CyPhPh5O2 4% 3CyPhPh5O2 4% 3CyCyPh5O3 7% 4CyCyPh5O2 7% 5CyCyPh5O2 7%3PhPh5O2 3% 4PhPh5O2 3% 5PhPh1 3% 3Cy2Cy3 15%  3CyDCy3 25%  0d3PhTPh3d02% 3CyPhTPh2 2% Drop mark evaluation B Ghosting evaluation B Responsespeed/ms 10.7

The liquid crystal display device of Comparative Example 2 was evaluatedin terms of ghosting and drop marks as in Example 1. The results areshown in Table 3.

The results show that the liquid crystal composition prepared inComparative Example 2 was inferior to the liquid crystal compositionprepared in Example 1. The liquid crystal composition prepared inComparative Example 2 exhibited a lower response speed than the liquidcrystal composition prepared in Example 1.

Comparative Example 3

A liquid crystal composition having a composition shown in Table 4 wasprepared and a liquid crystal display device of Comparative Example 3was obtained as in Example 1 except that this liquid crystal compositionwas used.

TABLE 4 T_(NI)/° C. 81.1 Δn 0.104 n₀ 1.488 ε_(//) 3.7 ε_(⊥) 6.5 Δε −2.9η/mPa · s 26.6 γ₁/mPa · s 146 γ₁/Δn² × 10⁻² 135 3CyCy2 24%  3CyCy4 79% 3CyPhO1 23%  3PhPh5Ph2 5% 4PhPh5Ph2 5% 3Cy1ONd4O4 3% 5Cy1ONd4O2 3%5Cy1ONd4O3 2% 3Cy2Cy1ONd4O2 7% 3Cy2Cy1ONd4O3 7% 2CyCy1ONd4O2 7%3CyCy1ONd4O4 7% Drop mark evaluation B Ghosting evaluation C Responsespeed/ms 11.1

The liquid crystal display device of Comparative Example 3 was evaluatedin terms of ghosting and drop marks as in Example 1. The results areshown in Table 4.

The results show that the liquid crystal composition prepared inComparative Example 3 was inferior to the liquid crystal compositionprepared in Example 1. The liquid crystal composition prepared inComparative Example 3 exhibited a lower response speed than the liquidcrystal composition prepared in Example 1.

Comparative Example 4

A liquid crystal composition having a composition shown in Table 5 wasprepared and a liquid crystal display device of Comparative Example 4was obtained as in Example 1 except that this liquid crystal compositionwas used.

TABLE 5 T_(NI)/° C. 79.9 Δn 0.104 n₀ 1.486 ε_(//) 3.7 ε_(⊥) 6.5 Δε −2.9η/mPa · s 29.7 γ₁/mPa · s 144 γ₁/Δn² × 10⁻² 132 3CyCy2 24%  3CyCy4 2%3CyPhO1 19%  3PhPh5Ph2 6% 4PhPh5Ph2 6% 3Cy1ONd4O4 3% 5Cy1ONd4O2 3%5Cy1ONd4O3 2% 3Cy2Cy1ONd4O2 4% 3Cy2Cy1ONd4O3 4% 2CyCy1ONd4O2 4%3CyCy1ONd4O4 4% 3Cy2Ph5O4 2% 4Cy2Ph5O2 2% 3CyCy2Ph5O3 5% 3CyCy2Ph5O4 5%3CyCy2Ph5O2 5% Drop mark evaluation C Ghosting evaluation B Responsespeed/ms 10.9

The liquid crystal display device of Comparative Example 4 was evaluatedin terms of ghosting and drop marks as in Example 1. The results areshown in Table 5.

The results show that the liquid crystal composition prepared inComparative Example 4 was inferior to the liquid crystal compositionprepared in Example 1. The liquid crystal composition prepared inComparative Example 4 exhibited a lower response speed than the liquidcrystal composition prepared in Example 1.

Comparative Example 5

A liquid crystal composition having a composition shown in Table 6 wasprepared and a liquid crystal display device of Comparative Example 5was obtained as in Example 1 except that this liquid crystal compositionwas used.

TABLE 6 T_(NI)/° C. 80.2 Δn 0.093 n₀ 1.484 ε_(//) 3.9 ε_(⊥) 7.7 Δε −3.7η/mPa · s 30.5 γ₁/mPa · s 153 γ₁/Δn² × 10⁻² 175 3CyCy2 24%  3CyCy4 6%3CyPhO1 25%  3Cy1ONd4O4 5% 5Cy1ONd4O2 5% 5Cy1ONd4O3 5% 3Cy2Cy1ONd4O2 8%3Cy2Cy1ONd4O3 8% 2CyCy1ONd4O2 7% 3CyCy1ONd4O4 7% Drop mark evaluation BGhosting evaluation C Response speed/ms 14.1

The liquid crystal display device of Comparative Example 5 was evaluatedin terms of ghosting and drop marks as in Example 1. The results areshown in Table 6.

The results show that the liquid crystal composition prepared inComparative Example 5 was inferior to the liquid crystal compositionprepared in Example 1. The liquid crystal composition prepared inComparative Example 5 exhibited a lower response speed than the liquidcrystal composition prepared in Example 1.

Comparative Example 6

A liquid crystal composition having a composition shown in Table 7 wasprepared and a liquid crystal display device of Comparative Example 6was obtained as in Example 1 except that this liquid crystal compositionwas used.

TABLE 7 T_(NI)/° C. 80.7 Δn 0.089 n₀ 1.482 ε_(//) 3.7 ε_(⊥) 6.8 Δε −3.1η/mPa · s 29.9 γ₁/mPa · s 130 γ₁/Δn² × 10⁻² 164 3CyCy2 24%  3CyCy4 2%3CyPhO1 25%  3Cy1ONd4O4 2% 5Cy1ONd4O2 2% 5Cy1ONd4O3 2% 3Cy2Cy1ONd4O2 6%3Cy2Cy1ONd4O3 6% 2CyCy1ONd4O2 6% 3CyCy1ONd4O4 5% 3Cy2Ph5O4 2% 4Cy2Ph5O22% 3CyCy2Ph5O3 5% 3CyCy2Ph5O4 6% 3CyCy2Ph5O2 5% Drop mark evaluation CGhosting evaluation C Response speed/ms 13.2

The liquid crystal display device of Comparative Example 6 was evaluatedin terms of ghosting and drop marks as in Example 1. The results areshown in Table 7.

The results show that the liquid crystal composition prepared inComparative Example 6 was inferior to the liquid crystal compositionprepared in Example 1. The liquid crystal composition prepared inComparative Example 6 exhibited a lower response speed than the liquidcrystal composition prepared in Example 1.

Example 2

A liquid crystal display device of Example 2 was obtained as in Example1 except that an N-methyl-pyrrolidone solution containing 3% of apolyimide derivative represented by formula below and 3% of apolymerizable compound having a reactive group represented by formula(V-3) below was used as the vertical alignment film forming material.

The liquid crystal display device of Example 2 was evaluated in terms ofghosting and drop marks as in Example 1. The results are shown in Table8.

The results show that the liquid crystal display device of Example 2 wasslightly inferior to the liquid crystal display device of Example 1 butexhibited high response speed, suppressed drop marks, and was resistantto ghosting.

TABLE 8 Drop mark evaluation AA Ghosting evaluation A Response speed/ms8.7

Example 3

A liquid crystal display device of Example 3 was obtained as in Example1 except that an N-methyl-2-pyrrolidone solution containing 3% of apolyimide derivative represented by formula below and 3% of apolymerizable compound having a reactive group represented by formula(V-4) below was used as the vertical alignment film forming material.

The liquid crystal display device of Example 3 was evaluated in terms ofghosting and drop marks as in Example 1. The results are shown in Table9.

The results show that the liquid crystal display device of Example 3 wasslightly inferior to the liquid crystal display device of Example 1 butexhibited high response speed, suppressed drop marks, and was resistantto ghosting.

TABLE 9 Drop mark evaluation A Ghosting evaluation AA Response speed/ms8.8

Example 4

A liquid crystal display device of Example 4 was obtained as in Example1 except that a liquid crystal composition having a composition shown inTable 10 was used as the liquid crystal composition.

TABLE 10 T_(NI)/° C. 80.2 Δn 0.105 n₀ 1.485 ε_(//) 3.2 ε_(⊥) 6.1 Δε −2.9η/mPa · s 22.7 γ₁/mPa · s 124 γ₁/Δn² × 10⁻² 112 3CyCy2 20%  3CyCy4 10% 3CyPh5O2 7% 3CyPh5O4 7% 2CyPhPh5O2 6% 3CyPhPh5O2 7% 3CyCyPh5O3 7%4CyCyPh5O2 8% 5CyCyPh5O2 7% 3PhPh5Ph2 4% 4PhPh5Ph2 4% 5PhPh1 8% 3CyCyPh15% Drop mark evaluation A Ghosting evaluation A Response speed/ms 9.3

The liquid crystal display device of Example 4 was evaluated in terms ofghosting and drop marks as in Example 1. The results are shown in Table10.

The results show that the liquid crystal display device of Example 4 wasslightly inferior to the liquid crystal display device of Example 1 butexhibited relatively high response speed, suppressed drop marks, and wasresistant to ghosting.

Example 5

A liquid crystal display device of Example 5 was obtained as in Example1 except that a liquid crystal composition having a composition shown inTable 11 was used as the liquid crystal composition.

TABLE 11 T_(NI)/° C. 80.3 Δn 0.106 n₀ 1.486 ε_(//) 3.3 ε_(⊥) 6.2 Δε −2.9η/mPa · s 21.4 γ₁/mPa · s 121 γ₁/Δn² × 10⁻² 107 3CyCy2 23%  3CyCy4 5%3CyPhO1 7% 2CyPh5O2 8% 3CyPh5O4 7% 2CyPhPh5O2 7% 3CyPhPh5O2 9%3CyCyPh5O3 5% 4CyCyPh5O2 6% 5CyCyPh5O2 5% 3PhPh5Ph2 5% 4PhPh5Ph2 6%3CyCyPh1 7% Drop mark evaluation A Ghosting evaluation AA Responsespeed/ms 8.9

The liquid crystal display device of Example 5 was evaluated in terms ofghosting and drop marks as in Example 1. The results are shown in Table11.

The results show that the liquid crystal display device of Example 5 wasslightly inferior to the liquid crystal display device of Example 1 butexhibited relatively high response speed, suppressed drop marks, and wasresistant to ghosting.

Example 6

A liquid crystal display device of Example 6 was obtained as in Example1 except that a liquid crystal composition having a composition shown inTable 12 was used as the liquid crystal composition.

TABLE 12 T_(NI)/° C. 81.3 Δn 0.106 n₀ 1.483 ε_(//) 3.2 ε_(⊥) 6.0 Δε −2.8η/mPa · s 20.7 γ₁/mPa · s 117 γ₁/Δn² × 10⁻² 105 3CyCy2 21%  3CyCy4 12% 3CyCy5 5% 2CyPh5O2 7% 3CyPh5O4 8% 2CyPhPh5O2 7% 3CyPhPh5O2 7% 3CyCyPh5O35% 4CyCyPh5O2 5% 5CyCyPh5O2 5% 3PhPh5Ph2 7% 4PhPh5Ph2 8% 3CyCyPh1 3%Drop mark evaluation AA Ghosting evaluation A Response speed/ms 8.8

The liquid crystal display device of Example 6 was evaluated in terms ofghosting and drop marks as in Example 1. The results are shown in Table12.

The results show that the liquid crystal display device of Example 6 wasslightly inferior to the liquid crystal display device of Example 1 butexhibited relatively high response speed, suppressed drop marks, and wasresistant to ghosting.

Example 7

A liquid crystal display device of Example 7 was obtained as in Example1 except that a liquid crystal composition having a composition shown inTable 13 was used as the liquid crystal composition.

TABLE 13 T_(NI)/° C. 82.7 Δn 0.107 n₀ 1.486 ε_(//) 3.3 ε_(⊥) 6.3 Δε −3.0η/mPa · s 24.2 γ₁/mPa · s 141 γ₁/Δn² × 10⁻² 123 3CyCy2 24%  3CyCy4 5%3CyPhO1 6% 2CyPh5O2 5% 3CyPh5O4 5% 2CyPhPh5O2 7% 3CyPhPh5O2 9%3CyCyPh5O3 8% 4CyCyPh5O2 9% 5CyCyPh5O2 8% 3PhPh5Ph2 5% 4PhPh5Ph2 5%5PhPh1 4% Drop mark evaluation A Ghosting evaluation A Response speed/ms10.2

The liquid crystal display device of Example 7 was evaluated in terms ofghosting and drop marks as in Example 1. The results are shown in Table13.

The results show that the liquid crystal display device of Example 7 wasslightly inferior to the liquid crystal display device of Example 1 butexhibited relatively high response speed, suppressed drop marks, and wasresistant to ghosting.

REFERENCE SIGNS LIST

10 liquid crystal display device, 11 first substrate, 12 secondsubstrate, 13 liquid crystal composition layer, 14 common electrode, 15pixel electrode, 16 vertical alignment film, 17 vertical alignment film,18 color filter, 19 liquid crystal molecule

The invention claimed is:
 1. A liquid crystal display device,comprising: a first substrate that includes an electrode; a secondsubstrate that includes an electrode; a liquid crystal composition layercomprising a liquid crystal composition, the liquid crystal compositionlayer sandwiched between the first substrate and the second substrate,in which liquid crystal molecules in the liquid crystal compositionlayer are controlled by applying charges between the electrode of thefirst substrate and the electrode of the second substrate substantiallyvertically to the first substrate and the second substrate; and avertical alignment film disposed on at least one of the first substrateand the second substrate, wherein the vertical alignment film controlsan alignment direction of the liquid crystal molecules in the liquidcrystal composition layer to be substantially vertical to a surface ofthe first substrate and a surface of the second substrate that areadjacent to the liquid crystal composition layer, wherein the verticalalignment film contains a polymer made from a first polymerizablecompound, wherein the first polymerizable compound had a polyimideskeleton as a main chain and a crosslinkable functional group as a sidechain, wherein the liquid crystal composition constituting the liquidcrystal composition layer contains: 30 to 65 mass% of a compoundrepresented by general formula (I),

(In the formula, R¹ and R² each independently represent an alkyl grouphaving 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms,an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy grouphaving 2 to 8 carbon atoms; A represents a 1,4-phenylene group or atrans-1,4-cyclohexylene group; 1 represents 1 or 2; and when 1 is 2, thetwo A may be the same or different from each other); and a compoundrepresented by general formula (II-1) and a compound represented bygeneral formula (II-2), a total content of the compound represented bygeneral formula (II-1) and the compound represented by general formula(II-2) being 30 to 65 mass% in the liquid crystal composition,

(In the formula, R³ represents an alkyl group having 1 to 8 carbonatoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy grouphaving 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbonatoms; and R4 represents an alkyl group having 1 to 8 carbon atoms, analkenyl group having 4 to 8 carbon atoms, an alkoxy group having 1 to 8carbon atoms, or an alkenyloxy group having 3 to 8 carbon atoms), and;

(In the formula, R⁵ represents an alkyl group having 1 to 8 carbonatoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy grouphaving 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbonatoms; R⁶ represents an alkyl group having 1 to 8 carbon atoms, analkenyl group having 4 to 8 carbon atoms, an alkoxy group having 1 to 8carbon atoms, or an alkenyloxy group having 3 to 8 carbon atoms; and Brepresents a 1,4-phenylene group or a trans-1,4-cyclohexylene group). 2.The liquid crystal display device according to claim 1, comprising aplurality of pixels each including two or more domains with pretiltangles different from one another.
 3. The liquid crystal display deviceaccording to claim 1, wherein in the vertical alignment film, the mainchain is a thermosetting polyimide or a soluble polyimide.
 4. The liquidcrystal display device according to claim 1, wherein the first substrateincludes a common electrode and the second substrate includes a pixelelectrode driven by a thin film transistor.
 5. The liquid crystaldisplay device according to claim 4, wherein the pixel electrode hascomb-tooth slits that extend in four directions from the center of thepixel so as to form four domains in which the liquid crystal moleculesin the liquid crystal composition layer align in different directions.6. The liquid crystal display device according to claim 1, wherein theliquid crystal composition layer is formed by a dropping method.
 7. Theliquid crystal display device according to claim 1, wherein the liquidcrystal composition contains 30 to 50 mass% of the compound representedby general formula (I).
 8. The liquid crystal display device accordingto claim 1, wherein, in the vertical alignment film, a thermosettingpolyimide skeleton is at least one selected from the group consisting ofpolyamic acid, polyimide, polyamic acid ester, polyester, polyamide,polyorganosiloxane, a cellulose derivative, a polyacetal derivative, apolystyrene derivative, a poly(styrene-phenylmaleimide) derivative, anda poly(meth)acrylate derivative.
 9. The liquid crystal display deviceaccording to claim 1, wherein the liquid crystal composition furthercontains 5 to 20 mass% of a compound represented by formula (III)

(In the formula, R⁷ and R⁸ each independently represent an alkyl grouphaving 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms,an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy grouphaving 2 to 8 carbon atoms; Y¹ and Y² each independently represent ahydrogen atom or a fluorine atom; D, E, and F each independentlyrepresent a 1,4-phenylene group or trans-1,4-cyclohexylene; Z²represents a single bond, —OCH₂—, —OCO—, —CH₂O—, or —COO—; and nrepresents 0 or 1.).
 10. A method for producing a liquid crystal displaydevice, the method comprising: applying a vertical alignment material toat least one of a first substrate including a common electrode and asecond substrate including a pixel electrode, the vertical alignmentmaterial containing a first polymerizable compound, wherein the firstpolymerizable compound has a thermosetting polyimide or solublepolyimide skeleton as a main chain and a crosslinkable functional groupas a side chain; heating the applied vertical alignment material to forman alignment film; sandwiching a liquid crystal composition between thefirst substrate and the second substrate; and irradiating the alignmentfilm with an active energy ray while applying a voltage between thecommon electrode and the pixel electrode to polymerize the firstpolymerizable compound in the alignment film, wherein the liquid crystalcomposition contains: 30 to 65 mass% of a compound represented bygeneral formula (I),

(In the formula, R¹ and R² each independently represent an alkyl grouphaving 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms,an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy grouphaving 2 to 8 carbon atoms; A represents a 1,4-phenylene group or atrans-1,4-cyclohexylene group; 1 represents 1 or 2; and when 1 is 2, thetwo A may be the same or different from each other); and a compoundrepresented by general formula (II-1) and a compound represented bygeneral formula (II-2), a total content of the compound represented bygeneral formula (II-1) and the compound represented by general formula(II-2) being 30 to 65 mass% in the liquid crystal composition,

(In the formula, R³ represents an alkyl group having 1 to 8 carbonatoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy grouphaving 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbonatoms; and R⁴ represents an alkyl group having 1 to 8 carbon atoms, analkenyl group having 4 to 8 carbon atoms, an alkoxy group having 1 to 8carbon atoms, or an alkenyloxy group having 3 to 8 carbon atoms); and

(In the formula, R⁵ represents an alkyl group having 1 to 8 carbonatoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy grouphaving 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbonatoms; R⁶ represents an alkyl group having 1 to 8 carbon atoms, analkenyl group having 4 to 8 carbon atoms, an alkoxy group having 1 to 8carbon atoms, or an alkenyloxy group having 3 to 8 carbon atoms; and Brepresents a 1,4-phenylene group or a trans-1,4-cyclohexylene group),the total content of the compound represented by general formula (II-1).11. The method for producing a liquid crystal display device accordingto claim 10, wherein the active energy ray is ultraviolet light, theintensity of the ultraviolet light is 2 mW/cm⁻2 to 100 mW/cm⁻2 , and thetotal irradiation energy quantity is 10 J to 300 J.
 12. The method forproducing a liquid crystal display device according to claim 10, whereinthe liquid crystal composition further contains 5 to 20 mass% of thecompound represented by formula (III),

(In the formula, R⁷ and R⁸ each independently represent an alkyl grouphaving 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms,an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy grouphaving 2 to 8 carbon atoms; Y¹ and Y² each independently represent ahydrogen atom or a fluorine atom; D, E, and F each independentlyrepresent a 1,4-phenylene group or trans-1,4-cyclohexylene; Z²represents a single bond, —OCH₂—, —OCO—, —CH₂O—, or —COO—; and nrepresents 0 or 1.).
 13. The liquid crystal display device according toclaim 1, wherein the first polymerizable compound was cured underapplication of voltage between the first substrate and the secondsubstrate while sandwiching the liquid crystal composition layertherebetween, such that the liquid crystal molecules in the liquidcrystal composition layer are provided with a pretilt angle.
 14. Themethod for producing a liquid crystal display device according to claim10, wherein when irradiating the alignment film with the active energyray while applying the voltage between the common electrode and thepixel electrode to polymerize the first polymerizable compound in thealignment film, liquid crystal molecules in the liquid crystalcomposition layer are provided with a pretilt angle.
 15. The liquidcrystal display device according to claim 1, wherein the verticalalignment film further contains a second polymerizable compound.
 16. Themethod for producing a liquid crystal display device according to claim10, wherein the vertical alignment film further contains a secondpolymerizable compound.
 17. The liquid crystal display device accordingto claim 1, wherein the crosslinkable functional group of the firstpolymerizable compound is an alkenyl group.
 18. The method for producinga liquid crystal display device according to claim 10, wherein thecrosslinkable functional group of the first polymerizable compound is analkenyl group.